This invention relates generally to an engine and more particularly to the cooling of a piston by placing a fin within a cooling recess of the piston.
Internal combustion engine manufacturers continually strive to decrease the physical size of engines and increase the power output per cylinder. In doing so, the manufacturer strives to increase fuel economy, efficiency, and service life, while reducing emissions. One way of improving efficiency and reducing size has been to increase temperatures and pressures in the combustion chamber. However, such increased temperatures and pressures in the combustion chamber place higher stresses on the piston that may cause the piston to deform or wear and prematurely fail.
One of the primary means of overcoming these detrimental effects on the piston is increasing the efficiency of heat rejection from the piston. For example, many high output engines employ cooling of the underside of the piston by spraying a cooling medium against the underside of the piston. The cooling medium absorbs a portion of the heat from the piston, falls away from the piston to the pan, is cooled and recycled to cool the piston again. To ensure efficient cooling of the underside of the piston, the spray must be precisely directed and retained to best remain in contact with the underside of the piston and absorb heat therefrom.
A method of increasing the contact between the oil and the interior of the piston is by increasing the surface area of the interior of the piston, thereby providing more area for the oil to contact and absorb heat. U.S. Pat. No. 2,523,699 issued to G. A. Holt et al. on Sep. 26, 1950 shows a series of ribs projecting inwardly from the interior wall of the piston skirt. These ribs increase the heat dissipating area of the piston that is in contact with the oil as the oil is shaken by the reciprocating motion of the piston. The intricate piston design set forth in Holt, however, is very difficult to produce via forging or machining processes. Therefore, the piston disclosed in Holt is practical for use solely in casting processes. However, the casting process introduces impurities into the cast product. These impurities decrease the density of the product and thus decrease the product""s resistance to deformation at high temperatures and pressures.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present application, a piston has a top portion having a bowl and a periphery portion. The bowl has an annular bowl that is attached to and extends radially inward from the periphery portion. Each of the annular bowl and the periphery portion has an inner surface. The piston has an outer annular wall that extends axially from the periphery portion of the top portion of the piston. The outer annular wall has an inner surface. The annular bowl inner surface, the periphery portion inner surface, and the outer annular wall inner surface define a cooling gallery. The piston has at least one annular fin that extends from the cooling gallery.
In another aspect of the present application, a method of creating a piston includes providing a piston having a top portion and an outer annular wall as described above and introducing to the cooling gallery at least one annular fin.